Event Details:

UNB Physics Department Seminar

Thursday, Feb. 9, 2023 from 1:15 -2:15 p.m. on Microsoft Teams (Email physics@unb.ca for link).

Estimating the Precipitable Water Vapor (PWV) over Canadian high arctic region using Global Navigation Satellite System (GNSS)

Presented by Ebtesam Gabr

One of the most important variables for analyzing the world's climate systems is atmospheric water vapour, especially over high latitudes and the arctic where water vapour exhibits a large seasonal variability. In general, each 1° K rise in temperature increases the water vapour content by 7%, and the increase of water vapour, as a greenhouse gas, will accelerate climate warming. The federal government climate report which was released in 2019 as part of Canada in a changing climate stated that Canada's climate has warmed and will warm further in the future and both past and future warming in Canada is, on average, about double the magnitude of global warming. The main obstacle to precise weather and climate prediction using numerical models is the absence of comprehensive knowledge of the global distribution of atmospheric water vapor in space and time. Increasing the sparse spatial and temporal sampling of atmospheric water vapour observations in Canada is necessary. This need has been uniquely met by GNSS water vapour observations obtained from (GNSS) networks. Differential GPS (DGPS) techniques were the primary foundation for water vapour determination using GPS. But because the GPS stations need to be sufficiently spaced apart in the network to estimate the water vapour on each station, the sizeable inter-station distance requirement has limited the DGPS application in meteorology. The Precise Point Positioning (PPP) technique, an innovative replacement for the DGPS method, relies on un-differenced observations from a single GPS receiver helped by precise orbit and clock products. The Canadian High Arctic Ionosphere Network (CHAIN) now provides good coverage for the Canadian high altitude and arctic region with a growing number of GNSS stations every year. 

The research aims to investigate the characteristics of PWV using the GNSS technique over the Canadian arctic region. Nine GNSS receivers of CHAIN network stations distributed along a wide range of geographical latitudes ranging between 58° N - 80° N have been used in this study. The work in this research is divided into two parts; the first part is to validate the PWV-GNSS technique over the Canadian arctic. And this is done through comparison with three techniques: collocated Radiosonde stations, Water Vapour Climate Change Initiative (WVCCI) (a dataset of global long-term and stable satellite derived time series for 21 essential climate variables among them water vapour established by ESA), and generation ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-5 reanalyses dataset. The comparison with the three data sets showed a good agreement with PWV-GNSS measurements. In the second part, which investigates the characteristics of the GNSS-derived PWV, a comprehensive time series analysis (least-square spectral analysis) is performed to determine the spatio-temporal variations of the PWV, also seasonal and diurnal cycles are studied. 

Building: Online via Microsoft Teams